This invention relates to medical devices, and more particularly implantable intraluminal devices for placement in a patient's body lumen, such as a blood vessel, to maintain the patency thereof. These devices are useful in the treatment of atherosclerotic stenosis in blood vessels.
Implantable intraluminal devices, such as stents, are generally tubular-shaped devices which function to hold open a segment of a blood vessel, coronary artery, or other anatomical lumen. They are particularly suitable for use to support and hold back a dissected arterial lining that can occlude the fluid passageway in the vessel. Similarly, vascular grafts may be implanted in vessels to strengthen or repair the vessel, or used in an anastomosis procedure to connect vessels segments together.
Stents often require extreme flexibility so as to be capable of being transported through varying and tortuous turns and diameters of the vessel pathway prior to arriving at the desired stenotic site. Expandable stents are so designed. Typically, expandable stents are delivered in a collapsed form to the stenotic region, expanded from within by a dilation balloon, and the ability to remain expanded so as to continue holding open the vessel after the balloon has been withdrawn.
Many expandable stents, however, do not retain a fully expanded state after the balloon has been withdrawn. Many such stents have been known to recoil after the inflation procedure due to elastic properties of the stent and applied stenotic pressure. If the recoil is great enough, the stent may also, due to lack of frictional resistance holding it in place, become dislodged from its location and migrate downstream. On such occasions, adequate lumenal flow can therefore be jeopardized. As a result, another procedure is needed to address a stent opening that has been so reduced. Therefore, it is important that a stent have sufficient radial strength to hold open and maintain the patency of a coronary artery.
Additionally, an expandable stent with plastic properties may be severely limited as to the degree of expandability of the stent from a deformed state into a permanently expanded configuration. It is therefore desirable for an expandable stent not to be so limited by its plastic properties and instead rely on different means for support when expanded beyond its ability to retain a plastically expanded shape.
There have been efforts to address the need to rigidize a stent after delivery and expansion. Some efforts have included, for example, the deposition of transformable materials in a stent wall. The mixing of epoxy components, for example, inside the wall of a stent has been heretofore disclosed. For example, it is known in the art that a stent may be constructed with a wall formed with breakable internal partitions separating mixable epoxy components. Such a stent may be designed to be delivered in a non-expanded state, and is thereafter subject to expansion by the dilation balloon. Accordingly, the expansion of the stent breaks open the partition walls allowing the epoxy components to mix, thereby hardening the resulting composition. Such stents, however, suffer the shortcoming that performance is dependent upon satisfactory formation and breaking of the partitions and the adequate intermixing of the epoxy components after the partitions have broken down. In addition, the prior art contains a stent with premixed epoxy enclosed in the stent wall. However, the art discloses that the pre-mixing stage takes place prior to insertion of the stent into the lumenal cavity and therefore requires the stent to not only be dispatched rapidly to the lumenal site, but also expanded before the mixed epoxy hardens.
What has been needed and heretofore unavailable is an improved stent or vascular graft that has a low profile and a high degree of flexibility so that it can be advanced through tortuous passageways and may be then expanded and more efficiently stiffened to hold open the body lumen into which it is expanded. The present invention satisfies this need.